Placental proteins as tumor markers.

Among the three placental proteins discussed, HCG is the only clinically useful tumor marker, and the value of HCG measurements is restricted to patients with gestational and nongestational trophoblastic disease. In patients with gestational trophoblastic disease, HCG levels may serve as an adjunct for the diagnosis, provide prognostic information, and be an objective parameter to evaluate the effects of therapy. Little or no additional information is obtained from HPL or SP-1 measurements. In patients with germ cell neoplasms of the testis, HCG measurements add useful information for clinical staging and monitoring of therapy, although discordance between tumor growth and HCG levels can be found in patients whose tumors contain several different elements. Therefore, AFP measurements must be made as well in these patients to monitor disease activity. Neither HPL nor SP-1 measurements are useful in these patients. None of the placental proteins are useful for screening, as prognostic indicators, or for evaluating the effects of therapy in groups of patients with nontrophoblastic neoplasms. In some patients with nontrophoblastic malignancies, each of the markers may accurately reflect changes in tumor burden during therapy. However, the problems with specificity and sensitivity of the tests and the fact that the majority of patients whose tumors produce the hormone have circulating concentrations that are at the limits of detection of the assays decrease the utility of these measurements and render them cost-ineffective for routine patient care.